Option 1, the preferred option, employs three mutually
independent keys (K1 ≠ K2 ≠ K3 ≠ K1). It gives keyspace of
3 × 56 = 168 bits.
Option 2 employs two mutually independent keys and a third
key that is the same as the first key (K1 ≠ K2 and K3 = K1).
This gives keyspace of 2 × 56= 112 bits.
Option 3 is a key bundle of three identical keys (K1 = K2 =
K3). This option is equivalent to DES Algorithm.
In 3-DES the 3-times iteration is applied to increase the
encryption level and average time. It is a known fact that
3DES is slower than other block cipher methods [11, 18].